Short-term to Decadal-scale Sand Flat Morphodynamics and Sediment Balance of a Megatidal Bay: Insight from Multiple LiDAR Datasets

2019 ◽  
Vol 88 (sp1) ◽  
pp. 61 ◽  
Author(s):  
Franck Levoy ◽  
Edward J. Anthony ◽  
Job Dronkers ◽  
Olivier Monfort ◽  
Anne-Lise Montreuil
Keyword(s):  
Short Term ◽  
Sand Flat ◽  
Decadal Scale ◽  
Sediment Balance

scholarly journals Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

2014 ◽  
Vol 8 (4) ◽  
pp. 1497-1507 ◽  
Author(s):  
S. A. Khan ◽  
K. K. Kjeldsen ◽  
K. H. Kjær ◽  
S. Bevan ◽  
A. Luckman ◽  
...  
Keyword(s):  
Mass Balance ◽  
Little Ice Age ◽  
Ice Age ◽  
Short Term ◽  
Velocity Change ◽  
Outlet Glacier ◽  
Episodic Events ◽  
Highly Sensitive ◽  
Decadal Scale ◽  
Speed Up

Abstract. Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim and Kangerdlugssuaq glaciers from 10 to more than 80 years. We show that, although the frontal portion of Helheim Glacier thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, Kangerdlugssuaq Glacier underwent minor thinning of 40–50 m from 1981 to 1998 and major thinning of more than 100 m after 2003. Extending the record back to the end of the Little Ice Age (prior to 1930) shows no thinning of Helheim Glacier from its maximum extent during the Little Ice Age to 1981, while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to 265 m. Comparison of sub-surface water temperature anomalies and variations in air temperature to records of thickness and velocity change suggest that both glaciers are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. On century timescales, however, multiple external parameters (e.g. outlet glacier shape) may dominate the mass change. These findings suggest that special care must be taken in the projection of future dynamic ice loss.

Revisiting the existence of the global warming slowdown during the early 21st century

2021 ◽  
pp. 1-40
Keyword(s):  
Global Warming ◽  
Greenhouse Gas ◽  
Selection Bias ◽  
21St Century ◽  
Linear Trend ◽  
Warming Trend ◽  
Short Term ◽  
Early 21St Century ◽  
Decadal Scale ◽  
Global Temperature Change

Abstract There are heated debates on the existence of the global warming slowdown during the early 21st century. Although efforts have been made to clarify or reconcile the controversy over the issue, it is not explicitly addressed, restricting the understanding of global temperature change particularly under the background of increasing greenhouse-gas concentrations. Here, using extensive temperature datasets, we comprehensively reexamine the existence of the slowdown under all existing definitions during all decadal-scale periods spanning 1990-2017. Results show that the short-term linear-trend dependent definitions of slowdown make its identification severely suffer from the period selection bias, which largely explains the controversy over its existence. Also, the controversy is further aggravated by the significant impacts of the differences between various datasets on the recent temperature trend and the different baselines for measuring slowdown prescribed by various definitions. However, when the focus is shifted from specific periods to the probability of slowdown events, we find the probability is significantly higher in the 2000s than in the 1990s, regardless of which definition and dataset are adopted. This supports a slowdown during the early 21st century relative to the warming surge in the late 20th century, despite higher greenhouse-gas concentrations. Furthermore, we demonstrate that this decadal-scale slowdown is not incompatible with the centennial-scale anthropogenic warming trend, which has been accelerating since 1850 and never pauses or slows. This work partly reconciles the controversy over the existence of the warming slowdown and the discrepancy between the slowdown and anthropogenic warming.

scholarly journals The influence of decadal-scale variability on trends in long European streamflow records

2013 ◽  
Vol 10 (2) ◽  
pp. 1859-1896 ◽  
Author(s):  
J. Hannaford ◽  
G. Buys ◽  
K. Stahl ◽  
L. M. Tallaksen
Keyword(s):  
Eastern Europe ◽  
River Flow ◽  
Interdecadal Variability ◽  
Trend Detection ◽  
Quality Data ◽  
Mean Flow ◽  
Short Term ◽  
Decadal Scale ◽  
Multi Temporal

Abstract. This study seeks to provide a long-term context for the growing number of trend analyses which have been applied to river flows in Europe. Most studies apply trend tests to fixed periods, in relatively short (generally 1960s–present) records. This study adopts an alternative "multi-temporal" approach, whereby trends are fitted to every possible combination of start and end years in a record. The method is applied to 132 catchments with long (1932–2004) hydrometric records from northern and central Europe, which were chosen as they are minimally anthropogenically influenced and have good quality data. The catchments are first clustered into five regions, which are broadly homogenous in terms of interdecadal variability of annual mean flow. The multi-temporal trend approach was then applied to regional time series of different hydrological indicators (annual, monthly and high and low flows). The results reveal that the magnitude and even direction of short-term trends are heavily influenced by interdecadal variability. Some short-term trends revealed in previous studies are shown to be unrepresentative of long-term change. For example, previous studies have identified post-1960 river flow decreases in southern and eastern Europe: in parts of eastern Europe, these trends are resilient to study period, extending back to the 1930s; in southern France, longer records show evidence of positive trends which reverse from the 1960s. Recent (post-1960) positive trends in northern Europe are also not present in longer records, due to decadal variations influenced by the North Atlantic Oscillation. The results provide a long-term reference for comparison with published and future studies. The multi-temporal approach advocated here is recommended for use in future trend assessments, to help contextualise short-term trends. Future work should also attempt to explain the decadal-scale variations that drive short-term trends, and thus develop more sophisticated methods for trend detection that take account of interdecadal variability and its drivers.

scholarly journals Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

2014 ◽  
Vol 8 (1) ◽  
pp. 1257-1278
Author(s):  
S. A. Khan ◽  
K. K. Kjeldsen ◽  
K. H. Kjær ◽  
S. Bevan ◽  
A. Luckman ◽  
...  
Keyword(s):  
Mass Balance ◽  
Little Ice Age ◽  
Initial Conditions ◽  
Ice Age ◽  
Short Term ◽  
Episodic Events ◽  
Highly Sensitive ◽  
Decadal Scale ◽  
Speed Up

Abstract. Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance at the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim glacier (HG) and Kangerdlugssuaq glacier (KG) from 10 to more than 150 yr. We show that although the frontal portion of HG thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, KG was stable from 1981 to 1998 and experienced major thinning only after 2003. Extending the record back to the end of the Little Ice Age (ca. 1850) shows no significant thinning of HG from 1850 to 1981, while KG underwent substantial thinning of ~265 m. Analyses of their sensitivity to sub-surface water temperature anomalies and variations in air temperature suggest that both HG and KG are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. At century time-scales, however, multiple external parameters (e.g. outlet shape) dominate the mass change. These findings undermine attempts to use measurements over the last decade as initial conditions to project future dynamic ice loss.

scholarly journals The influence of decadal-scale variability on trends in long European streamflow records

2013 ◽  
Vol 17 (7) ◽  
pp. 2717-2733 ◽  
Author(s):  
J. Hannaford ◽  
G. Buys ◽  
K. Stahl ◽  
L. M. Tallaksen
Keyword(s):  
Eastern Europe ◽  
River Flow ◽  
Interdecadal Variability ◽  
Trend Detection ◽  
Quality Data ◽  
Mean Flow ◽  
Short Term ◽  
Decadal Scale ◽  
Multi Temporal

Abstract. This study seeks to provide a long-term context for the growing number of trend analyses which have been applied to river flows in Europe. Most studies apply trend tests to fixed periods, in relatively short (generally 1960s–present) records. This study adopts an alternative "multi-temporal" approach, whereby trends are fitted to every possible combination of start and end years in a record. The method is applied to 132 catchments with long (1932–2004) hydrometric records from northern and central Europe, which were chosen as they are minimally anthropogenically influenced and have good quality data. The catchments are first clustered into five regions, which are broadly homogenous in terms of interdecadal variability of annual mean flow. The multi-temporal trend approach was then applied to regional time series of different hydrological indicators (annual, monthly and high and low flows). The results reveal that the magnitude and even direction of short-term trends are heavily influenced by interdecadal variability. Some short-term trends revealed in previous studies are shown to be unrepresentative of long-term change. For example, previous studies have identified post-1960 river flow decreases in southern and eastern Europe: in parts of eastern Europe, these trends are resilient to study period, extending back to the 1930s; in southern France, longer records show evidence of positive trends which reverse from the 1960s. Recent (post-1960) positive trends in northern Europe are also not present in longer records, due to decadal variations influenced by the North Atlantic Oscillation. The results provide a long-term reference for comparison with published and future studies. The multi-temporal approach advocated here is recommended for use in future trend assessments, to help contextualise short-term trends. Future work should also attempt to explain the decadal-scale variations that drive short-term trends, and thus develop more sophisticated methods for trend detection that take account of interdecadal variability and its drivers.

Quantifying decadal-scale erosion rates and their short-term variability on ecological sites in a semi-arid environment

CATENA ◽  
2016 ◽  
Vol 137 ◽  
pp. 501-507 ◽  
Author(s):  
V.O. Polyakov ◽  
M.A. Nearing ◽  
J.J. Stone ◽  
C.D. Holifield Collins ◽  
M.H. Nichols
Keyword(s):  
Arid Environment ◽  
Short Term ◽  
Ecological Sites ◽  
Erosion Rates ◽  
Decadal Scale ◽  
Semi Arid ◽  
Short Term Variability

scholarly journals Predicting tidal heights for extreme environments: From 25 h observations to accurate predictions at Jang Bogo Antarctic Research Station, Ross Sea, Antarctica

2020 ◽  
Author(s):  
Do-Seong Byun ◽  
Deirdre E. Hart
Keyword(s):  
Ross Sea ◽  
Extreme Environments ◽  
Form Factors ◽  
Reference Station ◽  
Research Station ◽  
Phase Lag ◽  
Short Term ◽  
Decadal Scale ◽  
Antarctic Research ◽  
Mean Square Errors

Abstract. Accurate tidal height data for the seas around Antarctica are much needed, given the crucial role of tidal processes as represented in regional and global climate, ocean and marine cryosphere models. Though obtaining long term sea level records for traditional tidal predictions is extremely difficult around ice affected coasts. This study evaluates the ability of a relatively new, tidal species based approach, the Complete Tidal Species Modulation with Tidal Constant Corrections (CTSM+TCC) method, to accurately predict tides for a temporary tidal station in the Ross Sea, Antarctica using records from a nearby reference station characterized by a different regime. Predictions for the 'mixed, mainly diurnal' regimes of Jang Bogo Antarctic Research Station (JBARS) were made and evaluated based on summertime (2017; and 2018 to 2019) short-term (25 h) observations at this temporary station, along with tidal prediction data derived from yearlong observations (2013) from the nearby, 'diurnal' regime of Cape Roberts (ROBT). Results reveal the CTSM+TCC method can produce accurate (to within ~ 5 cm Root Mean Square Errors) tidal predictions for JBARS when using short-term (25 h) tidal data from periods with higher than average tidal ranges (i.e. tropic-spring periods). Predictions were successful due to the similar relationships between the main tidal constituents' (K1 and O1 tides) phase-lag differences at the prediction and reference stations, and despite these tidal stations being characterized by different tidal regimes according to their form factors (i.e. mixed, mainly diurnal versus diurnal). We demonstrate how to determine optimal short-term data collection periods based on the Moon's declination. The importance of using long period tides to improve tidal prediction accuracy is also considered, along with the characteristics of the different decadal scale tidal variations around Antarctica, from the four major FES2014 tidal harmonic constants.

scholarly journals Decadal-Scale Reduction in Forest Net Ecosystem Production Following Insect Defoliation Contrasts with Short-Term Impacts of Prescribed Fires

Forests ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 145 ◽  
Author(s):  
Kenneth Clark ◽  
Heidi Renninger ◽  
Nicholas Skowronski ◽  
Michael Gallagher ◽  
Karina Schäfer
Keyword(s):  
Net Ecosystem Production ◽  
Prescribed Fires ◽  
Short Term ◽  
Scale Reduction ◽  
Insect Defoliation ◽  
Decadal Scale ◽  
Ecosystem Production
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